Semiconductor Device and Method of Forming Sacrificial Protective Layer to Protect Semiconductor Die Edge During Singulation

ABSTRACT

A semiconductor wafer contains a plurality of semiconductor die separated by a saw street. An insulating layer is formed over the semiconductor wafer. A protective layer is formed over the insulating layer including an edge of the semiconductor die along the saw street. The protective layer covers an entire surface of the semiconductor wafer. Alternatively, an opening is formed in the protective layer over the saw street. The insulating layer has a non-planar surface and the protective layer has a planar surface. The semiconductor wafer is singulated through the protective layer and saw street to separate the semiconductor die while protecting the edge of the semiconductor die. Leading with the protective layer, the semiconductor die is mounted to a carrier. An encapsulant is deposited over the semiconductor die and carrier. The carrier and protective layer are removed. A build-up interconnect structure is formed over the semiconductor die and encapsulant.

CLAIM TO DOMESTIC PRIORITY

The present application is a continuation of U.S. patent applicationSer. No. 14/494,508, filed Sep. 23, 2014, which is a continuation ofU.S. patent application Ser. No. 13/446,664, now U.S. Pat. No.8,907,476, filed Apr. 13, 2012, which is a division of U.S. patentapplication Ser. No. 13/029,936, now U.S. Pat. No. 8,183,095, filed Feb.17, 2011, which claims the benefit of U.S. Provisional Application No.61/313,208, filed Mar. 12, 2010, which applications are incorporatedherein by reference.

FIELD OF THE INVENTION

The present invention relates in general to semiconductor devices and,more particularly, to a semiconductor device and method of forming atemporary planarization protective layer to protect a semiconductor dieedge during singulation.

BACKGROUND OF THE INVENTION

Semiconductor devices are commonly found in modern electronic products.Semiconductor devices vary in the number and density of electricalcomponents. Discrete semiconductor devices generally contain one type ofelectrical component, e.g., light emitting diode (LED), small signaltransistor, resistor, capacitor, inductor, and power metal oxidesemiconductor field effect transistor (MOSFET). Integrated semiconductordevices typically contain hundreds to millions of electrical components.Examples of integrated semiconductor devices include microcontrollers,microprocessors, charged-coupled devices (CCDs), solar cells, anddigital micro-mirror devices (DMDs).

Semiconductor devices perform a wide range of functions such as signalprocessing, high-speed calculations, transmitting and receivingelectromagnetic signals, controlling electronic devices, transformingsunlight to electricity, and creating visual projections for televisiondisplays. Semiconductor devices are found in the fields ofentertainment, communications, power conversion, networks, computers,and consumer products. Semiconductor devices are also found in militaryapplications, aviation, automotive, industrial controllers, and officeequipment.

Semiconductor devices exploit the electrical properties of semiconductormaterials. The atomic structure of semiconductor material allows itselectrical conductivity to be manipulated by the application of anelectric field or base current or through the process of doping. Dopingintroduces impurities into the semiconductor material to manipulate andcontrol the conductivity of the semiconductor device.

A semiconductor device contains active and passive electricalstructures. Active structures, including bipolar and field effecttransistors, control the flow of electrical current. By varying levelsof doping and application of an electric field or base current, thetransistor either promotes or restricts the flow of electrical current.Passive structures, including resistors, capacitors, and inductors,create a relationship between voltage and current necessary to perform avariety of electrical functions. The passive and active structures areelectrically connected to form circuits, which enable the semiconductordevice to perform high-speed calculations and other useful functions.

Semiconductor devices are generally manufactured using two complexmanufacturing processes, i.e., front-end manufacturing, and back-endmanufacturing, each involving potentially hundreds of steps. Front-endmanufacturing involves the formation of a plurality of die on thesurface of a semiconductor wafer. Each die is typically identical andcontains circuits formed by electrically connecting active and passivecomponents. Back-end manufacturing involves singulating individual diefrom the finished wafer and packaging the die to provide structuralsupport and environmental isolation.

One goal of semiconductor manufacturing is to produce smallersemiconductor devices. Smaller devices typically consume less power,have higher performance, and can be produced more efficiently. Inaddition, smaller semiconductor devices have a smaller footprint, whichis desirable for smaller end products. A smaller die size can beachieved by improvements in the front-end process resulting in die withsmaller, higher density active and passive components. Back-endprocesses may result in semiconductor device packages with a smallerfootprint by improvements in electrical interconnection and packagingmaterials.

A semiconductor wafer contains a plurality of semiconductor die orcomponents separated by a saw street. The semiconductor wafer issingulated through the saw street into individual semiconductor dieusing a saw blade or laser cutting tool. Once singulated, thesemiconductor die can be mounted to a temporary carrier in order to forma build-up interconnect structure for a fan-out wafer level chip scalepackage (Fo-WLCSP). The semiconductor die are subject to chipping andcracking along the die edge or other damage during the singulationprocess, more specifically by the impact of the spinning saw blade.Metal burring can occur along the saw street during singulation, whichcan cause electrical shorting when forming the build-up interconnectstructure. In situations where the semiconductor die has an uneven orhigh topology, the adhesion between the die and carrier can be weakleading to defects during the interconnect build-up process.

SUMMARY OF THE INVENTION

A need exists to protect the semiconductor die during singulation andprovide a planar surface between the die and carrier during the build-upinterconnect process. Accordingly, in one embodiment, the presentinvention is a method of making a semiconductor device comprising thesteps of providing a semiconductor die, forming a protective layer overthe semiconductor die, depositing an encapsulant over the semiconductordie, forming a first cavity in the encapsulant, removing the protectivelayer, and forming an interconnect structure over the semiconductor dieincluding a first insulating layer of the interconnect structureextending into the first cavity.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a semiconductordie, depositing an encapsulant over the semiconductor die, forming afirst cavity in the encapsulant adjacent to the semiconductor die, andforming an interconnect structure over the semiconductor die and intothe first cavity.

In another embodiment, the present invention is a method of making asemiconductor device comprising the steps of providing a semiconductordie, depositing an encapsulant over the semiconductor die, and forming afirst cavity in the encapsulant adjacent to the semiconductor die.

In another embodiment, the present invention is a semiconductor devicecomprising a semiconductor die. An encapsulant is deposited over thesemiconductor die. A first cavity is formed in the encapsulant adjacentto the semiconductor die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a PCB with different types of packages mounted to itssurface;

FIGS. 2a-2c illustrate further detail of the semiconductor packagesmounted to the PCB;

FIGS. 3a-3i illustrate process of forming a protective layer over anuneven insulating layer to planarize a semiconductor die and protect adie edge during singulation;

FIGS. 4a-4j illustrate a process of forming a WLCSP with thesemiconductor die having the sacrificial protective layer to planaruneven surfaces;

FIG. 5 illustrates a WLCSP with a shallow cavity formed in theencapsulant over the RDL and bumps;

FIG. 6 illustrates a WLCSP with a shallow circle cavity formed in theencapsulant over the RDL and bumps and encapsulant trim around thesemiconductor die;

FIG. 7 illustrates a WLCSP with shallow cavities formed in theencapsulant over the RDL and bumps and around the semiconductor die; and

FIG. 8 illustrates a WLCSP with shallow cavities formed in theencapsulant and thick RDL under the cavities.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention is described in one or more embodiments in thefollowing description with reference to the figures, in which likenumerals represent the same or similar elements. While the invention isdescribed in terms of the best mode for achieving the invention'sobjectives, it will be appreciated by those skilled in the art that itis intended to cover alternatives, modifications, and equivalents as maybe included within the spirit and scope of the invention as defined bythe appended claims and their equivalents as supported by the followingdisclosure and drawings.

Semiconductor devices are generally manufactured using two complexmanufacturing processes: front-end manufacturing and back-endmanufacturing. Front-end manufacturing involves the formation of aplurality of die on the surface of a semiconductor wafer. Each die onthe wafer contains active and passive electrical components, which areelectrically connected to form functional electrical circuits. Activeelectrical components, such as transistors and diodes, have the abilityto control the flow of electrical current. Passive electricalcomponents, such as capacitors, inductors, resistors, and transformers,create a relationship between voltage and current necessary to performelectrical circuit functions.

Passive and active components are formed over the surface of thesemiconductor wafer by a series of process steps including doping,deposition, photolithography, etching, and planarization. Dopingintroduces impurities into the semiconductor material by techniques suchas ion implantation or thermal diffusion. The doping process modifiesthe electrical conductivity of semiconductor material in active devices,transforming the semiconductor material into an insulator, conductor, ordynamically changing the semiconductor material conductivity in responseto an electric field or base current. Transistors contain regions ofvarying types and degrees of doping arranged as necessary to enable thetransistor to promote or restrict the flow of electrical current uponthe application of the electric field or base current.

Active and passive components are formed by layers of materials withdifferent electrical properties. The layers can be formed by a varietyof deposition techniques determined in part by the type of materialbeing deposited. For example, thin film deposition can involve chemicalvapor deposition (CVD), physical vapor deposition (PVD), electrolyticplating, and electroless plating processes. Each layer is generallypatterned to form portions of active components, passive components, orelectrical connections between components.

The layers can be patterned using photolithography, which involves thedeposition of light sensitive material, e.g., photoresist, over thelayer to be patterned. A pattern is transferred from a photomask to thephotoresist using light. In one embodiment, the portion of thephotoresist pattern subjected to light is removed using a solvent,exposing portions of the underlying layer to be patterned. In anotherembodiment, the portion of the photoresist pattern not subjected tolight, the negative photoresist, is removed using a solvent, exposingportions of the underlying layer to be patterned. The remainder of thephotoresist is removed, leaving behind a patterned layer. Alternatively,some types of materials are patterned by directly depositing thematerial into the areas or voids formed by a previous deposition/etchprocess using techniques such as electroless and electrolytic plating.

Depositing a thin film of material over an existing pattern canexaggerate the underlying pattern and create a non-uniformly flatsurface. A uniformly flat surface is required to produce smaller andmore densely packed active and passive components. Planarization can beused to remove material from the surface of the wafer and produce auniformly flat surface. Planarization involves polishing the surface ofthe wafer with a polishing pad. An abrasive material and corrosivechemical are added to the surface of the wafer during polishing. Thecombined mechanical action of the abrasive and corrosive action of thechemical removes any irregular topography, resulting in a uniformly flatsurface.

Back-end manufacturing refers to cutting or singulating the finishedwafer into the individual die and then packaging the die for structuralsupport and environmental isolation. To singulate the die, the wafer isscored and broken along non-functional regions of the wafer called sawstreets or scribes. The wafer is singulated using a laser cutting toolor saw blade. After singulation, the individual die are mounted to apackage substrate that includes pins or contact pads for interconnectionwith other system components. Contact pads formed over the semiconductordie are then connected to contact pads within the package. Theelectrical connections can be made with solder bumps, stud bumps,conductive paste, or wirebonds. An encapsulant or other molding materialis deposited over the package to provide physical support and electricalisolation. The finished package is then inserted into an electricalsystem and the functionality of the semiconductor device is madeavailable to the other system components.

FIG. 1 illustrates electronic device 50 having a chip carrier substrateor printed circuit board (PCB) 52 with a plurality of semiconductorpackages mounted on its surface. Electronic device 50 can have one typeof semiconductor package, or multiple types of semiconductor packages,depending on the application. The different types of semiconductorpackages are shown in FIG. 1 for purposes of illustration.

Electronic device 50 can be a stand-alone system that uses thesemiconductor packages to perform one or more electrical functions.Alternatively, electronic device 50 can be a subcomponent of a largersystem. For example, electronic device 50 can be part of a cellularphone, personal digital assistant (PDA), digital video camera (DVC), orother electronic communication device. Alternatively, electronic device50 can be a graphics card, network interface card, or other signalprocessing card that can be inserted into a computer. The semiconductorpackage can include microprocessors, memories, application specificintegrated circuits (ASIC), logic circuits, analog circuits, RFcircuits, discrete devices, or other semiconductor die or electricalcomponents. Miniaturization and weight reduction are essential for theseproducts to be accepted by the market. The distance betweensemiconductor devices must be decreased to achieve higher density.

In FIG. 1, PCB 52 provides a general substrate for structural supportand electrical interconnect of the semiconductor packages mounted on thePCB. Conductive signal traces 54 are formed over a surface or withinlayers of PCB 52 using evaporation, electrolytic plating, electrolessplating, screen printing, or other suitable metal deposition process.Signal traces 54 provide for electrical communication between each ofthe semiconductor packages, mounted components, and other externalsystem components. Traces 54 also provide power and ground connectionsto each of the semiconductor packages.

In some embodiments, a semiconductor device has two packaging levels.First level packaging is a technique for mechanically and electricallyattaching the semiconductor die to an intermediate carrier. Second levelpackaging involves mechanically and electrically attaching theintermediate carrier to the PCB. In other embodiments, a semiconductordevice may only have the first level packaging where the die ismechanically and electrically mounted directly to the PCB.

For the purpose of illustration, several types of first level packaging,including bond wire package 56 and flip chip 58, are shown on PCB 52.Additionally, several types of second level packaging, including ballgrid array (BGA) 60, bump chip carrier (BCC) 62, dual in-line package(DIP) 64, land grid array (LGA) 66, multi-chip module (MCM) 68, quadflat non-leaded package (QFN) 70, and quad flat package 72, are shownmounted on PCB 52. Depending upon the system requirements, anycombination of semiconductor packages, configured with any combinationof first and second level packaging styles, as well as other electroniccomponents, can be connected to PCB 52. In some embodiments, electronicdevice 50 includes a single attached semiconductor package, while otherembodiments call for multiple interconnected packages. By combining oneor more semiconductor packages over a single substrate, manufacturerscan incorporate pre-made components into electronic devices and systems.Because the semiconductor packages include sophisticated functionality,electronic devices can be manufactured using cheaper components and astreamlined manufacturing process. The resulting devices are less likelyto fail and less expensive to manufacture resulting in a lower cost forconsumers.

FIGS. 2a-2c show exemplary semiconductor packages. FIG. 2a illustratesfurther detail of DIP 64 mounted on PCB 52. Semiconductor die 74includes an active region containing analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed within the die and are electricallyinterconnected according to the electrical design of the die. Forexample, the circuit can include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements formedwithin the active region of semiconductor die 74. Contact pads 76 areone or more layers of conductive material, such as aluminum (Al), copper(Cu), tin (Sn), nickel (Ni), gold (Au), or silver (Ag), and areelectrically connected to the circuit elements formed withinsemiconductor die 74. During assembly of DIP 64, semiconductor die 74 ismounted to an intermediate carrier 78 using a gold-silicon eutecticlayer or adhesive material such as thermal epoxy or epoxy resin. Thepackage body includes an insulative packaging material such as polymeror ceramic. Conductor leads 80 and bond wires 82 provide electricalinterconnect between semiconductor die 74 and PCB 52. Encapsulant 84 isdeposited over the package for environmental protection by preventingmoisture and particles from entering the package and contaminating die74 or bond wires 82.

FIG. 2b illustrates further detail of BCC 62 mounted on PCB 52.Semiconductor die 88 is mounted over carrier 90 using an underfill orepoxy-resin adhesive material 92. Bond wires 94 provide first levelpackaging interconnect between contact pads 96 and 98. Molding compoundor encapsulant 100 is deposited over semiconductor die 88 and bond wires94 to provide physical support and electrical isolation for the device.Contact pads 102 are formed over a surface of PCB 52 using a suitablemetal deposition process such as electrolytic plating or electrolessplating to prevent oxidation. Contact pads 102 are electricallyconnected to one or more conductive signal traces 54 in PCB 52. Bumps104 are formed between contact pads 98 of BCC 62 and contact pads 102 ofPCB 52.

In FIG. 2c , semiconductor die 58 is mounted face down to intermediatecarrier 106 with a flip chip style first level packaging. Active region108 of semiconductor die 58 contains analog or digital circuitsimplemented as active devices, passive devices, conductive layers, anddielectric layers formed according to the electrical design of the die.For example, the circuit can include one or more transistors, diodes,inductors, capacitors, resistors, and other circuit elements withinactive region 108. Semiconductor die 58 is electrically and mechanicallyconnected to carrier 106 through bumps 110.

BGA 60 is electrically and mechanically connected to PCB 52 with a BGAstyle second level packaging using bumps 112. Semiconductor die 58 iselectrically connected to conductive signal traces 54 in PCB 52 throughbumps 110, signal lines 114, and bumps 112. A molding compound orencapsulant 116 is deposited over semiconductor die 58 and carrier 106to provide physical support and electrical isolation for the device. Theflip chip semiconductor device provides a short electrical conductionpath from the active devices on semiconductor die 58 to conductiontracks on PCB 52 in order to reduce signal propagation distance, lowercapacitance, and improve overall circuit performance. In anotherembodiment, the semiconductor die 58 can be mechanically andelectrically connected directly to PCB 52 using flip chip style firstlevel packaging without intermediate carrier 106.

FIGS. 3a-3i illustrate, in relation to FIGS. 1 and 2 a-2 c, a process offorming a temporary protective layer over an uneven insulating layer toplanarize a semiconductor die and protect a die edge during singulation.FIG. 3a shows a semiconductor wafer 120 with a base substrate material122, such as silicon, germanium, gallium arsenide, indium phosphide, orsilicon carbide, for structural support. A plurality of semiconductordie or components 124 is formed on wafer 120 separated by saw streets126 as described above.

FIG. 3b shows a cross-sectional view of a portion of semiconductor wafer120. Each semiconductor die 124 has a back surface 128 and activesurface 130 containing analog or digital circuits implemented as activedevices, passive devices, conductive layers, and dielectric layersformed within the die and electrically interconnected according to theelectrical design and function of the die. For example, the circuit mayinclude one or more transistors, diodes, and other circuit elementsformed within active surface 130 to implement analog circuits or digitalcircuits, such as digital signal processor (DSP), ASIC, memory, or othersignal processing circuit. Semiconductor die 124 may also containintegrated passive devices (IPDs), such as inductors, capacitors, andresistors, for RF signal processing. In one embodiment, semiconductordie 124 is a flipchip type semiconductor die.

An electrically conductive layer 132 is formed over active surface 130using PVD, CVD, electrolytic plating, electroless plating process, orother suitable metal deposition process. Conductive layer 132 can be oneor more layers of Al, Cu, Sn, Ni, Au, Ag, or other suitable electricallyconductive material. In one embodiment, conductive layer 132 extendsabove active surface 130 by 0.6 micrometers (μm) or more. Conductivelayer 132 operates as contact pads electrically connected to thecircuits on active surface 130.

In FIG. 3c , an insulating or passivation layer 134 is conformallyapplied over active surface 130 and conductive layer 132 using PVD, CVD,screen printing, spin coating, spray coating, sintering or thermaloxidation. The insulating layer 134 contains one or more layers ofsilicon dioxide (SiO2), silicon nitride (Si3N4), silicon oxynitride(SiON), tantalum pentoxide (Ta2O5), aluminum oxide (Al2O3), polyimide,polybenzoxazoles (PBO), polymer dielectric material, or other materialhaving similar insulating and structural properties. In one embodiment,insulating layer 134 has a thickness greater than 0.6 μm. The insulatinglayer 134 is noted as having a first portion 134 a over active surface130 and second portion 134 b over conductive layer 132. The secondportion 134 b has a high topology with respect to active surface 130 dueto the conformal application of insulating layer 134 over conductivelayer 132. Accordingly, insulating layer 134 generally has an uneventopology or non-planar surface. A portion of insulating layer 134 b isremoved to expose conductive layer 132, as shown in FIG. 3d . A portionof insulating layer 134 b remains over conductive layer 132, causing theuneven topology or non-planar surface of insulating layer 134.

In FIG. 3e , a blanket temporary protective planarization layer 136 isformed over insulating layer 134 and conductive layer 132 while in waferform using screen printing, spin coating, spray coating, and lamination.After depositing temporary protective planarization layer 136,additional treatment, such as UV exposure and heat process, can beapplied to provide necessary adhesion and mechanical properties. Thetemporary protective planarization layer 136 contains one or more layersof photoresist, liquid coating material, dry film, polymer film, polymercomposite, or other material having properties of compliance, structuresupport, planarization capability, thermal stability under 110-160° C.for 5 to 120 minutes, and easy strip after encapsulating process.Protective planarization layer 136 is a temporary or sacrificial layerused to planarize the uneven topology of insulating layer 134. Thetemporary protective planarization layer 136 fills in around the unevenportions of insulating layer 134 to make a planar surface 135. In oneembodiment, temporary protective planarization layer 136 is 5 to 25 μmin thickness.

In one embodiment, temporary protective planarization layer 136 coversthe entire surface of semiconductor wafer or substrate 120 withoutpatterning, including semiconductor die 124 and saw streets 126, asshown in FIG. 3f . In FIG. 3g , semiconductor wafer 120 is singulatedthrough insulating layer 134, temporary protective planarization layer136, and saw street 126 using a saw blade or laser cutting tool 137 intoindividual semiconductor die 124.

Alternatively, temporary protective planarization layer 136 is patternedto have trench or groove 138 formed over saw streets 126, as shown inFIG. 3h . The width of trench 138 (W_(T)) is less than the width of sawstreets 126 (W_(S)), e.g., W_(T) is made 10 μm less than W_(S), withtemporary protective planarization layer 136 overlapping saw streets 126by at least 5 μm on each side. The width of saw blade or laser cuttingtool 137 is shown as dimension W_(C). If a conductive layer 139 isformed over saw street 126, then W_(T) is made 10 μm less than a widthof the widest portion of conductive layer 139, with temporary protectiveplanarization layer 136 overlapping conductive layer 139 by at least 5μm on each side.

A laser can be used to form trench or groove 138 in saw street 126 byremoving metal, insulating material, and base semiconductor materialwith 2-7 passes. The laser reduces cracking of the insulating material,particularly for low dielectric constant (k) material, which can occurduring mechanical dicing with saw blade or cutting tool 137. Thetemporary protective planarization layer 136 is deposited over sawstreet 126 prior to laser excitation. Protective planarization layer 136provides for convenient control of the dielectric thickness foradditional protection of semiconductor die 124 in reliability testing.In addition, temporary protective planarization layer 136 helps toprevent the die shift and flying die issue in late encapsulating processin FIG. 4c . A thick temporary protective planarization layer 136 alsohelps to prevent wafer surface from dicing dust blasting and damage inmechanical dicing process.

FIG. 3i shows an alternate pattern of openings 140 with notches 141. Inany case, temporary protective planarization layer 136 protects the kerfedge of semiconductor die 124 from chipping and cracking, as well assuppressing metal burring and delamination along saw street 126 or edgeof the die, during singulation.

FIGS. 4a-4j illustrate, in relation to FIGS. 1 and 2 a-2 c, a process offorming a WLCSP with the semiconductor die having the sacrificialprotective layer to planar uneven surfaces. FIG. 4a shows a portion ofsubstrate or carrier 142 containing temporary or sacrificial basematerial such as steel, iron alloy, silicon, polymer, beryllium oxide,or other suitable low-cost, rigid material for structural support. Aninterface layer or double-sided tape 144 is formed over carrier 142 as atemporary adhesive bonding film or etch-stop layer. In one embodiment,interface layer 144 is thermal or light releasable.

Semiconductor die 124 from FIGS. 3a-3i is positioned over and mounted tocarrier 142 using a pick and place operation. FIG. 4b showssemiconductor die 124 mounted to carrier 142 with planar surface 135 oftemporary protective planarization layer 136 oriented toward interfacelayer 144 and carrier 142. Planar surface 135 of temporary protectiveplanarization layer 136 enhances the adhesion or bonding strength ofsemiconductor die 124 to interface layer 144 by increasing the effectivecontact surface area and minimizing void forming between the surface ofsemiconductor die 124 and interface layer 144. Carrier 142 extendsbeyond the dimensions shown in FIG. 4b for a wafer-level multi-dieattachment. Many semiconductor die 124 can be mounted to carrier 142.

In FIG. 4c , an encapsulant or molding compound 146 is deposited oversemiconductor die 124 and interface layer 144 with temporary protectiveplanarization layer 136 present using a paste printing, compressivemolding, transfer molding, liquid encapsulant molding, vacuumlamination, spin coating, or other suitable applicator. Encapsulant 146can be polymer composite material, such as epoxy resin with filler,epoxy acrylate with filler, or polymer with proper filler. Encapsulant146 is non-conductive and environmentally protects the semiconductordevice from external elements and contaminants.

In FIG. 4d , carrier 142 and interface layer 144 are removed by chemicaletching, mechanical peel-off, CMP, mechanical grinding, thermal bake,laser scanning, or wet stripping to expose temporary protectiveplanarization layer 136 and encapsulant 146.

The temporary protective planarization layer 136 is removed by peeling,as shown in FIG. 4e . Alternatively, temporary protective planarizationlayer 136 can be removed with deionized (DI) water spray and rinse or bysolvent or chemical stripping. Temporary protective planarization layer136 provides a number of advantageous features for semiconductor die124, including reducing die edge chipping and cracking during waferdicing, reducing flying die during encapsulation, reducing conductivebur formation during wafer dicing, easy control over dielectricthickness, and reducing dust damage on active surface 130 during waferdicing.

In another embodiment, continuing from FIG. 4d , backgrinding tape 150is applied to encapsulant 146 and temporary protective planarizationlayer 136, as shown in FIG. 4f . A portion of surface 152 of encapsulant146 is removed by grinder 154 to planarize the encapsulant and exposeback surface 128 of semiconductor die 124. Temporary protectiveplanarization layer 136 is then removed with backgrinding tape 150 afterthe grinding operation, leaving back surface 128 of insulating layer 134and conductive layer 132 exposed, as shown in FIG. 4 g.

In FIG. 4h , an insulating or passivation layer 156 is formed oversurface 158 of encapsulant 152, opposite surfaces 128 and 152, usingPVD, CVD, screen printing, spin coating, spray coating, sintering orthermal oxidation. The insulating layer 156 contains one or more layersof polyimide, benzocyclobutene (BCB), PBO, low temperature (<280° C.)curing polymer dielectric, or other material having similar insulatingand structural properties. A portion of insulating layer 156 is removedto expose conductive layer 132.

In FIG. 4i , an electrically conductive layer or redistribution layer(RDL) 160 is formed over insulating layer 156 and conductive layer 132using a patterning and metal deposition process such as PVD, CVD,sputtering, electrolytic plating, and electroless plating. Conductivelayer 160 can be one or more layers of Al, Cu, Ti/Cu, TiW/Cu, Sn, Ni,Au, Ag, or other suitable electrically conductive material. Conductivelayer 160 is electrically connected to conductive layer 132.

An insulating or passivation layer 162 is formed over insulating layer156 and conductive layer 160 using PVD, CVD, screen printing, spincoating, spray coating, sintering or thermal oxidation. The insulatinglayer 162 contains one or more layers of polyimide, BCB, PBO, lowtemperature (<280° C.) curing polymer dielectric, or other materialhaving similar insulating and structural properties. A portion ofinsulating layer 162 is removed to expose conductive layer 160.Additional RDL layers, including conductive and insulation layers, maybe built up as per design requirements.

In FIG. 4j , an electrically conductive bump material is deposited overthe exposed conductive layer 160 using an evaporation, electrolyticplating, electroless plating, ball drop, or screen printing process. Thebump material can be Al, Sn, Ni, Au, Ag, Pb, Bi, Cu, solder, andcombinations thereof, with an optional flux solution. For example, thebump material can be eutectic Sn/Pb, high-lead solder, or lead-freesolder. The bump material is bonded to conductive layer 160 using asuitable attachment or bonding process. In one embodiment, the bumpmaterial is reflowed by heating the material above its melting point toform spherical balls or bumps 164. In some applications, bumps 164 arereflowed a second time to improve electrical contact to conductive layer160. The bumps can also be compression bonded to conductive layer 160.Bumps 164 represent one type of interconnect structure that can beformed over conductive layer 160. The interconnect structure can alsouse stud bump, micro bump, or other electrical interconnect.

FIG. 5 shows another embodiment, similar to FIG. 4j , with shallowcavity or channel 170 formed in encapsulant 146 under conductive layer160 and bumps 164. The shallow cavity 170 can be formed by laserdrilling encapsulant 146 in FIG. 4d to a depth of 5-50 μm, prior toremoval of temporary protective planarization layer 136. The shallowcavity 170 provides dumping support in drop test (DT) and temperaturecycling on board (TCoB) test. Shallow cavity 170 also enhancesrepassivation with insulating layer 156.

FIG. 6 shows another embodiment, similar to FIG. 4j , with shallowcircle cavity or channel 172 formed in encapsulant 146 aroundsemiconductor die 124 under conductive layer 160 and bumps 164. Theshallow circle cavity 172 can be formed by laser drilling encapsulant146 in FIG. 4d to a depth of 5-50 μm, prior to removal of temporaryprotective planarization layer 136. The shallow circle cavity 172provides dumping support in DT and TCoB test. In addition, the laser cantrim edge 174 of encapsulant 146 around semiconductor die 142 in FIG. 4d, prior to removal of temporary protective planarization layer 136.

FIG. 7 shows another embodiment, similar to FIG. 4j , with shallowcavity or channel 178 formed in encapsulant 146 around semiconductor die124 under conductive layer 160 and bumps 164. In addition, shallowcavity or channel 180 is formed in encapsulant 146 around the edge ofsemiconductor die 124. The shallow cavities 178-180 can be formed bylaser drilling encapsulant 146 in FIG. 4d to a depth of 5-50 μm, priorto removal of temporary protective planarization layer 136. The shallowcavities 178-180 provide dumping support in DT and TCoB test.

FIG. 8 shows another embodiment, similar to FIG. 4j , with shallowcavity or channel 182 formed in encapsulant 146 around semiconductor die124 under conductive layer 160 and bumps 164. In addition, shallowcavity or channel 184 is formed in encapsulant 146 around the edge ofsemiconductor die 124. The shallow cavities 182-184 can be formed bylaser drilling encapsulant 146 in FIG. 4d to a depth of 5-50 μm, priorto removal of temporary protective planarization layer 136. The shallowcavities 182-184 provide dumping support in DT and TCoB test. Theinsulating layer 156 has sufficient thickness to form dishing overshallow cavities 182 without fully planarizing the substrate surface.Conductive layer 160 has a thicker dome-shaped portion 186 under shallowcavities 182 and 184.

While one or more embodiments of the present invention have beenillustrated in detail, the skilled artisan will appreciate thatmodifications and adaptations to those embodiments may be made withoutdeparting from the scope of the present invention as set forth in thefollowing claims.

What is claimed:
 1. A method of making a semiconductor device,comprising: providing a semiconductor die; forming a protective layerover the semiconductor die; depositing an encapsulant over thesemiconductor die; forming a first cavity in the encapsulant; removingthe protective layer; and forming an interconnect structure over thesemiconductor die including a first insulating layer of the interconnectstructure extending into the first cavity.
 2. The method of claim 1,further including forming the first cavity by laser drilling.
 3. Themethod of claim 1, further including: forming a second insulating layerover the semiconductor die including a non-planar surface of the secondinsulating layer opposite the semiconductor die; and forming theprotective layer over the second insulating layer.
 4. The method ofclaim 1, wherein the first cavity extends to the semiconductor die. 5.The method of claim 1, further including forming a second cavity in thefirst insulating layer aligned with the first cavity.
 6. The method ofclaim 5, wherein the interconnect structure further includes aconductive layer deposited into the second cavity.
 7. A method of makinga semiconductor device, comprising: providing a semiconductor die;depositing an encapsulant over the semiconductor die; forming a firstcavity in the encapsulant adjacent to the semiconductor die; and formingan interconnect structure over the semiconductor die and into the firstcavity.
 8. The method of claim 7, further including forming the firstcavity by laser drilling.
 9. The method of claim 7, wherein forming theinterconnect structure includes depositing an insulating layer over thesemiconductor die and into the first cavity.
 10. The method of claim 9,further including forming a second cavity in the insulating layer overthe first cavity.
 11. The method of claim 10, wherein forming theinterconnect structure further includes depositing a conductive layerinto the second cavity.
 12. The method of claim 7, further includingforming a second cavity in the encapsulant and extending to thesemiconductor die, wherein the second cavity is between the first cavityand semiconductor die.
 13. A method of making a semiconductor device,comprising: providing a semiconductor die; depositing an encapsulantover the semiconductor die; and forming a first cavity in theencapsulant adjacent to the semiconductor die.
 14. The method of claim13, further including forming the first cavity by laser drilling. 15.The method of claim 13, further including depositing an insulating layerover the semiconductor die and into the first cavity.
 16. The method ofclaim 15, further including forming a second cavity in the insulatinglayer over the first cavity.
 17. The method of claim 16, furtherincluding depositing a conductive layer into the second cavity.
 18. Themethod of claim 13, further including forming a second cavity in theencapsulant and extending to the semiconductor die.
 19. The method ofclaim 18, wherein the second cavity extends around an edge of thesemiconductor die.
 20. A semiconductor device, comprising: asemiconductor die; an encapsulant deposited over the semiconductor die;and a first cavity formed in the encapsulant adjacent to thesemiconductor die.
 21. The semiconductor device of claim 20, furtherincluding an insulating layer formed over the semiconductor die andextending into the first cavity.
 22. The semiconductor device of claim21, further including a second cavity formed in the insulating layerover the first cavity.
 23. The semiconductor device of claim 22, furtherincluding a conductive layer deposited in the second cavity.
 24. Thesemiconductor device of claim 20, further including a second cavityformed in the encapsulant and extending to the semiconductor die. 25.The semiconductor device of claim 24, wherein the second cavity extendsaround an edge of the semiconductor die.